Magnetic switch chopper



April 26, 1960 o. J. STEWART 2,934,621

MAGNETIC SWITCH CHOPPER Filed Dec. 12, 1958 f3 J I 23 2 22 5e 34 I A iza/i3 43 3 7 5 s I 27 23 22 la INVENTOR. DONALD J. STEWART ATT RNEYS United States Patent ,0 l ce 2,934,621 MAGNETIC SWITCH CHOPPER Donald J. Stewart, National City, Calif. Application December 12, 1958, Serial No. 780,174

11 Claims. (Cl. 200-90) (Granted under Title 35, US. Code (1952), sec. 266) The switch operates by sensing the magnetic polarity of a magnetic field, which may be changing at a high frequency, and can be used, for instance, to produce a square wave or a half wave in an electronic circuit. This switch may also be used as an ordinary on-off switch in almost unlimited applications, and can be operated in circuits which are subjected to high gravitational forces and vibrations. The present magnetic-field actuated switch will operate satisfactorily from one to greater than two thousand contacts per second.

Previously, switches had leads connected directly to 'the moving parts, had contact bounce, were subject to changes in operation caused by acceleration forces, and i required screw thread adjustments and adjustable pivots.

The present invention is of very simple construction and may be made in extremely small sizes, and overcomes all the above disadvantages of the prior art switches.

' This invention consists of a permanent magnet barshaped' armature which pivots on a pair of ball bearings Within a housing that also acts as the armature contact to ground. One end of the armature carries a pair of [contact wires which alternately contact respective stationary contacts in the housing cover. The magnetic switch is operated by a magnetic field of alternating polarity, such as a spinning. magnet or an oscillating field coil nearby which attracts and repels the poles of the permanent magnet armature causing it to rock in its pivot at a frequency directly proportional to the frelquency of the change of polarity of the magnetic field and thus cause the contact wires to make and break contact with their respective stationary contacts at the same rate of frequency.

.It is an object of the invention therefore to provide a new and improved electronic chopper.

It is another object of the present invention to provide a magnetic-field actuated high-frequency switch.

" Still another object of the invention is to provide a ,single-pole double-throw switch which will operate from zero to high frequency satisfactorily even when subjected ;to high gravitational forces and vibrations.

' A further object of the invention is to provide magnetic polarity sensing chopping switch for rapid on-ofi operation.

, A still further object of the invention is to provide a simply constructed switch for producing square waves or half waves in an electronic circuit.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by-reference to the fol- 14, as shown in Fig. 1.

Patented Apr. 26, 1960 lowing detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a cross-sectional longitudinal view of the magnetic switch of the present invention;

Fig. 2 is cross-sectional view of the magnetic switch taken along line 22 of Fig. 1;

Fig. 3 is anothercross-sectional longitudinal view of the magnetic switch, taken along line 3-3 of Fig. 1;

Fig. 4 is a cross-sectional view of the magnetic switch taken along line 44 of Fig. 3;

, Fig. 5 shows a diagrammatic sketch of the operation of the switch with a magnetic field attracting the armature toward one contact.

Referring now to the drawings, like numerals refer to like partsin each of the figures.

. The magnetic switch comprises a non-magnetic housing consisting of a base portion 10 and a closure portion 12, as shown in Figs. 1 and 3, both portions are made from a non-magnetic and electrically conductive material such as brass, for example. An armature comprising a bar-shaped permanent magnet 14 is mounted for rocking at its center of gravity on ball bearings 16 within base portion 10 of the housing. Ball bearings 16 are supported in apertures 18 in base portion 10 and in turn support permanent magnet 14 by partially fitting within apertures 20 in magnet holder ring 21. The ball bearings 16 are held in place by spring load retainer ring 22 which fits in peripheral groove 23 about base portion 10 and bears against the ball bearings with sufiicient pressure to firmly hold them in place. Groove 23 has portions 24 and 25 removed therefrom to allow spring action to retainer ring 22; ball bearings 16 distend retainer ring 22 to increase its diameter along the axis passing through the two ball bearings and spaces 24 and 25 in groove 23 allow the diameter of retainer ring 22 to decrease along the axis perpendicular to the first mentioned axis. Spaces 24 and 25 compensate for dimensional changes due to changes in temperature and/or original fabrication. A U-shaped wire 26 which forms a pair of moving contacts 27 and 28 fits about permanent magnet Wire 26 is held in place on magnet 14 by holder ring 21; the arms of the U-shaped wire fit within grooves 30 in the holder ring. The contact ends of the arms of the U-shaped wire 26 are bent slightly away from magnet 14 at 31 and 32.

Closure portion 12 of the switch housing has a disk 34 of electrically insulative material mounted at the inner end thereof; a small dish shaped depression 35 is formed therein to provide clearance for the N-pole end of magnet 14 and the ends of contacts 27 and 28. A spacer 36 of electrically non-conductive material is provided within ,closure portion 12. One edge of spacer 36 rests in grooves 38 at the inner end of base portion 10. Spacer 36 properly positions disk 34 from the end of magnet 14.

Disk 34 carries stationary contacts 40 and 41 mounted thereon. Electrical lead wires 43 and 44 pass through apertures in closure portion 12 and are connected to stationary contacts 40 and 41 respectively. Stationary contacts 40 and 41 may be merely extensions of lead wires 43 and 44 which pass through disk 34 and bend at to be parallel with the fiat surface of the disk on the side facing magnet 14, and then have their ends bend at 90 back into disk 34 for support, as illustrated in Figs. 1 and 4. Lead wires 43 and 44 are each provided with a sheath 46 of electrically insulative material where they pass through closure portion 12 to properly insulate the wires from the housing. Insulation 46 also seals the openings in closure portion 12 through which wires 43 and 44 pass. Base portion 10 and closure portion 12 fit together so as to form a hermetically sealed structure. The housing portions 10 and 12, ball bearings 16, magnet holder 21 andmagnet 14 all form an electrical-path between contacts 27 and 28 and ground wire 50 which is fastened to the end of closure portion 12. A notch 52 is provided in the base end of base portion this notch is parallel with the pivot axis through ball bearings 16 and is used for properly aligning movable contacts 27 and 28 with stationary contacts 40 and 41 when assembling the switch.

The magnetic switch operates as follows: Magnet 14 is free to pivot or rock back and forth on ball bearings 16 about its center of gravity when attracted or repelled by a magnetic field. As illustrated in Fig. 5, by way of example, a rotating magnet 55 is provided near the end of the magnetic switch, as described hereinabove, so that the switch lies within the effective magnetic field of the magnet 55. When the S-pole of magnet 55, as it rotates about its center pivot 56, approaches the magnetic switch, the N-pole of magnet 14 will be attracted to move in a direction causing movable contact 27 to come into contact with stationary contact 41. In like manner as the N-pole of rotating magnet 55 comes close to the'magnetic switch, the N-pole of magnet 14 will be repelled and move in a direction towards stationary contact 40 causing movable contact 28 to come into contact with stationary contact 40. Thus when the S-pole of rotating magnet 55 is nearest the magnetic switch the circuit is completed between ground wire 50 and lead wire 44, and when the N-pole of magnet 55 is close to the magnetic switch the circuit is completed between ground wire 50 and lead wire 43.

The hereinabove described magnetic switch has no lead wires connected directly to the moving parts; all lead wires are exterior of the housing, and the switch may be potted or enclosed in a vacuum tube type of mounting for potting or atmosphere control. Damping or response of the switch can be controlled by the tension of spring load retaining ring 22, and the switch will operate during high acceleration forces and vibrations. The fast response time of this switch can be adjusted to no-olf time, that is, to make before break or any other combination of square wave configuration, by adjusting the gap between the contacts or by changing the strength of the magnetic field; further, frequency has small effect on square wave configuration. The switch will respond to frequencies from 0 to more than 1000 cycles per second and due to its construction will not resonate at any of these frequencies. The switch can be made very small in size and has been made as small as. .150 inch by .250 inch.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A switch assembly operated by an external magnetic field and operable to sense the polarity and changes in polarity thereof, comprising a switch housing, an armature assembly having pivot means mounted within said housing, said armature assembly operable to rockingly pivot at its center of gravity within said housing, said armature assembly comprising a bar-shaped permanent magnet having a pair of electrical contacts mounted on opposite sides of one end thereof, both of said pair of electrical contacts being electrically connected through said magnet to an electrical ground terminal, the end of said housing adjacent the end of said magnet carrying the pair of electrical contacts having first and second stationary contacts mounted therein, said stationary contacts being mounted such that when said magnet rocks in one direction the first of said pair of contacts on the magnet will contact the first stationary contact, and when the magnet rocks in the other direction the second of said pair of contacts thereon will contact the second stationary contact, whereby the changing polarity of a magnetic field nearby will attract and repel one end of the bar magnet of said armature assembly at a frequency directly proportional to the change in polarity of said magnetic field nearby thus causing the switch to change contact with each change of polarity of the magnetic field nearby.

2. A switch as in claim 1 wherein said magnet, pivot means and housing act as an electrically conductive path between said electrical contacts on said magnet and said ground terminal, said housing being made of a nonmagnetic material.

3. A switch as in claim 1 wherein said pivot means has a damping means applied thereto for maintaining said pivot means under load and for damping said armature assembly. 7

4. A switch as in claim 3 wherein said pivot means comprises a pair of pivot balls supported by said housing and in turn which support said armature assembly.

5. A switch as in claim 4 wherein said damping means comprises a retaining ring which keeps said pivot balls engaged under load by applying friction damping to. said armature assembly.

6. A switch assembly operated by an external magnetic field and operable to sense the polarity and changes in polarity thereof, comprising a switch housing, an armature having pivot means at its center of gravity mounted within said housing, said armature operable to rockingly pivot within said housing, said armature comprising a bar-shaped permanent magnet which acts as a common contact and is electrically connected to an electrical ground terminal, an end of said housing adjacent one end of said armature magnet having first and second stationary contacts mounted therein, said stationary contacts being mounted such that when said magnet rocks in one direction it will contact the first of said stationary contacts and when the magnet rocks in the opposite direction it will contact the second of said stationary contacts, whereby the changing polarity of a magnetic field nearby will attract and repel one end of said armature magnet at a frequency directly proportional to the change in polarity of said magnetic field nearby thus causing the bar magnet to change contact with each change of polarity of the magnetic field nearby.

7. A switch as in claim 6 wherein said pivot, means comprises ball bearings supported by said housing and means for applying damping means to said armature.

8. A switch assembly operated by an external magnetic field and operable to sense the polarity and changes in polarity thereof, comprising a switch housing, an armature having pivot means at its center of gravity and supported thereby, said pivot means comprising a pair of pivot balls which are supported by said. housing and in turn support said armature, said armature operable to rockingly pivot within said housing, said armature comprising a bar-shaped magnet which acts as a common contact and is electrically connected to an electrical ground terminal, an end of said housing adjacent one end of said armature magnet having first and second stationary contacts mounted therein, each stationary contact being electrically connected to an exterior terminal, said stationary contacts being mounted in said housing such that when said magnet rocks in one direction it will contact the first of said stationary contacts and when the magnet rocks in the opposite direction it will contact; the second of said stationary contacts, whereby the changing polarity of a magnetic field nearby will attract and repel one end of said armature magnet at a frequency directly proportional to the change in polarity of said magnetic field nearby thus causing the bar magnet to change contact with each change of polarity of the magnetic field nearby.

9. A switch as in claim 8v wherein a retaining ring keeps said pivot balls engaged under load and thus applies a friction damping to said armature,

10. A switch as in claim 8 wherein said housing is hermetically sealed.

11. A magnetically-influenced electrical switch adapted to provide selective switching action in accordance with sense of magnetic field direction, said switch comprising, in combination: a pair of inner and outer generally tubular sections associated to provide an elongated housing; an armature assembly contained within said housing, said armature assembly including a magnetized bar-shaped armature having opposite poles at the ends thereof, and a ring clamped upon said armature between the poles thereof; a pair of ball bearings contained between said ring and said inner tubular section and supporting said armature for pivotal movement about a transverse axis; at least one movable contact secured by said ring to said armature for movement therewith; at least one stationary complementary contact supported by and insulated from said housing; and said ring, ball bearings and housing being electrically conductive and providing electrical con- 5 tinuity between said movable contact and said housing.

References Cited in the file of this patent UNITED STATES PATENTS 

